Front-end module and communication device

ABSTRACT

A front-end module includes a switch, a first filter including an input end connected to a first selection terminal, a second filter including input end connected to a second selection terminal, and an impedance matching circuit connected to a selection terminal, a pass band impedance when viewing the first filter side from a common terminal in a state in which the common terminal and only the first selection terminal are connected is different from a pass band impedance when viewing the second filter side from the common terminal in a state that the common terminal and only the second selection terminal are connected. When the common terminal and the first selection terminal are connected, the common terminal and the selection terminal are connected, and when the common terminal and the second selection terminal are connected, the common terminal and the selection terminal are not connected.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication No. 2017-190340 filed on Sep. 29, 2017. The entire contentsof this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a front-end module and a communicationdevice.

2. Description of the Related Art

In recent years, a mobile communication terminal has been desired toenable multi-band in which one terminal supports a plurality offrequency bands. Accordingly, for example, a front-end circuit disposedbetween an antenna element and an amplifier is also desired to enablethe multi-band.

Japanese Unexamined Patent Application Publication No. 2015-61198discloses a multi-band-supported front end circuit which includes aswitch and four filters disposed between a common antenna and twotransmission amplification circuits and two reception amplifiercircuits. An impedance matching circuit including an inductor isprovided in each signal path connecting the switch and each filter.

However, when an individual impedance matching circuit is provided foreach signal path as in the front end circuit disclosed in JapaneseUnexamined Patent Application Publication No. 2015-61198, the number ofcircuit elements defining the impedance matching circuit increases andthe front end circuit becomes large in size in accordance with anadvance of the multi-band (an increase in the number of supportedbands). Further, signal transmission loss increases for each signalpath.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide front-end modulesand communication devices in which the signal transmission loss and thenumber of circuit elements are reduced.

According to a preferred embodiment of the present invention, afront-end module includes a first switch including a first commonterminal and a plurality of selection terminals; a first filterincluding a first frequency band as a pass band, a first input/outputterminal, and a second input/output terminal, the first input/outputterminal being connected to a first selection terminal among theplurality of selection terminals; a second filter including a secondfrequency band different from the first frequency band as a pass band, athird input/output terminal, and a fourth input/output terminal, thethird input/output terminal being connected to a second selectionterminal among the plurality of selection terminals; and a firstimpedance matching circuit connected to one or more selection terminalsdifferent from the first selection terminal and the second selectionterminal among the plurality of selection terminals. An impedance in thefirst frequency band when viewing a first filter side from the firstcommon terminal in a state that the first common terminal is connectedto only the first selection terminal among the plurality of selectionterminals is different from an impedance in the second frequency bandwhen viewing a second filter side from the first common terminal in astate that the first common terminal is connected to only the secondselection terminal among the plurality of selection terminals. When thefirst common terminal is in a connection state with the first selectionterminal and the first common terminal is in a non-connection state withthe second selection terminal, the first common terminal is in aconnection state with one selection terminal among the one or moreselection terminals, and when the first common terminal is in aconnection state with the second selection terminal and the first commonterminal is in a non-connection state with the first selection terminal,the first common terminal is in a non-connection state with the oneselection terminal.

According to the above-described configuration, when the first switchand the first filter are connected, since the first impedance matchingcircuit is connected on a path connecting the first switch and the firstfilter with the one selection terminal interposed therebetween, animpedance when viewing the first filter side from the first commonterminal is able to be adjusted to a predetermined impedance. On theother hand, when the first switch and the second filter are connected,the first impedance matching circuit is not connected on the pathconnecting the first switch and the first filter with the one selectionterminal interposed therebetween. In this case, although the connectionstate of the first impedance matching circuit on the above-describedpath is different, since an impedance in the first frequency band whenviewing the first filter side from the first common terminal in a statethat the first common terminal and the first selection terminal areconnected is different from an impedance in the second frequency bandwhen viewing the second filter side from the first common terminal in astate that the first common terminal and the second selection terminalare connected, the impedance when viewing the second filter side fromthe first common terminal is able to be adjusted to the predeterminedimpedance.

Therefore, it is possible to reduce loss of signal transmission and thenumber of circuit elements as compared to a front-end module of therelated art in which an impedance matching circuit is provided for eachsignal path between a first switch and a filter.

Further, a front-end module according to a preferred embodiment of thepresent invention may further include a second impedance matchingcircuit connected to the first common terminal.

In both cases when the first filter is selected and when the secondfilter is selected, an impedance when viewing each filter side from thefirst common terminal is able to be adjusted to the predeterminedimpedance. By connecting the second impedance matching circuit, eachimpedance when viewing each filter side from a corresponding node isable to be matched to a normalized impedance of the front-end module.

In addition, a first wire connecting the first filter and the firstselection terminal may be longer than a second wire connecting thesecond filter and the second selection terminal, and an impedance in thefirst frequency band when viewing the first filter alone from the firstinput/output terminal and an impedance in the second frequency band whenviewing the second filter alone from the third input/output terminal maybe higher than the normalized impedance of the front-end module, and thefirst impedance matching circuit may include an inductor connectedbetween the one or more selection terminals and a ground.

Thus, in a state in which the first common terminal and the secondfilter are connected, the impedance when viewing the second filter sidefrom the first common terminal becomes an impedance which is shifted tobe more capacitive than an impedance of the second filter alone due toparasitic capacitance of the second wire and the first switch.

On the other hand, in a state in which the first common terminal and thefirst filter are connected, the impedance when viewing the first filterside from the first common terminal becomes an impedance which isshifted to be furthermore capacitive than an impedance in a state inwhich the first common terminal is connected to the second filter due toparasitic capacitance of the first wire longer than the second wire andthe first switch. However, since a shunt inductor defining the firstimpedance matching circuit is connected, the impedance when viewing thefirst filter side from the first common terminal is shiftedcounterclockwise along an equiconductance circle on an immittance chart,and thus, is equal or substantially equal to an impedance when viewingthe second filter side from the first common terminal in a state inwhich the first common terminal and the second filter are connected.

In addition, the first impedance matching circuit may include a firstparallel matching circuit connected between a third selection terminalamong the plurality of selection terminals and the ground, and the firstswitch may exclusively switch between conduction between the firstselection terminal and the first common terminal and conduction betweenthe second selection terminal and the first common terminal and mayswitch between conduction and non-conduction between the third selectionterminal and the first common terminal.

Accordingly, the first parallel matching circuit is able to beshunt-connected on a path connecting the first common terminal and thefirst filter or the second filter. Thus, an impedance when viewing thefilter side from the first common terminal is able to be matched to theabove-described predetermined impedance.

In addition, the first impedance matching circuit may further include asecond parallel matching circuit connected between a fourth selectionterminal among the plurality of selection terminals and the ground, andthe first switch may exclusively switch between conduction between thefirst selection terminal and the first common terminal and conductionbetween the second selection terminal and the first common terminal, mayswitch between conduction and non-conduction between the third selectionterminal and the first common terminal, and may switch betweenconduction and non-conduction between the fourth selection terminal andthe first common terminal.

Accordingly, the first parallel matching circuit and/or the secondparallel matching circuit is able to be shunt-connected on the pathconnecting the first common terminal and the first filter or the secondfilter. Thus, the impedance when viewing the filter side from the firstcommon terminal is able to be matched in a wide band and with a highdegree of accuracy.

In addition, the first impedance matching circuit may include a firstseries matching circuit connected between a fifth selection terminal anda sixth selection terminal among the plurality of selection terminals,and the first switch may exclusively switch between one of connectionbetween the first selection terminal and the first common terminal andconduction between the first selection terminal and the first commonterminal via the sixth selection terminal, the first series matchingcircuit, and the fifth selection terminal, and one of connection betweenthe second selection terminal and the first common terminal andconduction between the second selection terminal and the first commonterminal via the sixth selection terminal, the first series matchingcircuit, and the fifth selection terminal.

Accordingly, the first series matching circuit is able to be inserted inseries on the path connecting the first common terminal and the firstfilter or the second filter. Thus, the impedance when viewing the filterside from the first common terminal is able to be matched with a highdegree of accuracy.

In addition, the first impedance matching circuit may further include asecond series matching circuit connected between a seventh selectionterminal and an eighth selection terminal among the plurality ofselection terminals, and the sixth selection terminal and the seventhselection terminal are connected. The first switch may exclusivelyswitch between one of connection between the first selection terminaland the first common terminal, conduction between the first selectionterminal and the first common terminal via the sixth selection terminal,the first series matching circuit, and the fifth selection terminal,conduction between the first selection terminal and the first commonterminal via the eighth selection terminal, the second series matchingcircuit, and the seventh selection terminal, and conduction between thefirst selection terminal and the first common terminal via the fifthselection terminal, the first series matching circuit, the sixthselection terminal, the seventh selection terminal, the second seriesmatching circuit, and the eighth selection terminal; and one ofconnection between the second selection terminal and the first commonterminal, conduction between the second selection terminal and the firstcommon terminal via the sixth selection terminal, the first seriesmatching circuit, and the fifth selection terminal, conduction betweenthe second selection terminal and the first common terminal via theeighth selection terminal, the second series matching circuit, and theseventh selection terminal, and conduction between the second selectionterminal and the first common terminal via the fifth selection terminal,the first series matching circuit, the sixth selection terminal, theseventh selection terminal, the second series matching circuit, and theeighth selection terminal.

Accordingly, the first series matching circuit and/or the second seriesmatching circuit is able to be inserted in series on the path connectingthe first common terminal and the first filter or the second filter.Thus, output impedance of a first amplifier and a second amplifier isable to be matched in a wide band and with a high degree of accuracy.

Further, a front-end module according to a preferred embodiment of thepresent invention may include a second switch including a second commonterminal, a ninth selection terminal, and a tenth selection terminal,and an amplifier connected to the second common terminal, and the secondinput/output terminal and the ninth selection terminal may be connected,the fourth input/output terminal and the tenth selection terminal may beconnected, and the second switch may switch between connection andnon-connection between the amplifier and the first filter, and mayswitch between connection and non-connection between the amplifier andthe second filter.

As a result, it is possible to provide a front-end module in which lossof signal transmission and the number of circuit elements are reduced.

Further, according to a preferred embodiment of the present invention, acommunication device includes an RF signal processing circuit thatprocesses a high-frequency signal received by an antenna element, andone of the above-described front-end modules according to preferredembodiments of the present invention that transmits the high-frequencysignal between the antenna element and the RF signal processing circuit.

As a result, it is possible to provide communication devices in whichloss of signal transmission and the number of circuit elements arereduced.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a circuit diagram of a communication device and an antennaelement in a connection configuration 1 according to a preferredembodiment of the present invention.

FIG. 1B is a circuit diagram of a communication device and an antennaelement in a connection configuration 2 according to a preferredembodiment of the present invention.

FIG. 2 is a circuit diagram of a front-end module according to acomparative example.

FIG. 3A is a circuit diagram of a front-end module and an antennaelement in a connection configuration 1 according to Example 1.

FIG. 3B is a diagram illustrating a change in an impedance at each nodeof the front-end module according to Example 1.

FIG. 4 is a circuit diagram of a front-end module and an antenna elementaccording to Modification 1 of a preferred embodiment of the presentinvention.

FIG. 5A is a circuit diagram of a front-end module and an antennaelement in a connection configuration 1 according to Modification 2 of apreferred embodiment of the present invention.

FIG. 5B is a circuit diagram of a front-end module and an antennaelement in a connection configuration 2 according to Modification 2.

FIG. 5C is a circuit diagram of a front-end module and an antennaelement in a connection configuration 3 according to Modification 2.

FIG. 6A is a circuit diagram of a front-end module and an antennaelement in a connection configuration 1 according to Modification 3 of apreferred embodiment of the present invention.

FIG. 6B is a circuit diagram of a front-end module and an antennaelement in a connection configuration 2 according to Modification 3.

FIG. 6C is a circuit diagram of a front-end module and an antennaelement in a connection configuration 3 according to Modification 3.

FIG. 7A is a circuit diagram of a front-end module and an antennaelement in a connection configuration 1 according to Modification 4 of apreferred embodiment of the present invention.

FIG. 7B is a circuit diagram of a front-end module and an antennaelement in a connection configuration 2 according to Modification 4.

FIG. 7C is a circuit diagram of a front-end module and an antennaelement in a connection configuration 3 according to Modification 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to examples, modifications, acomparative example, and drawings. Each of the following examples andmodifications represents a comprehensive or specific example. Numericalvalues, shapes, materials, components, arrangement and connectionconfigurations of components and other features and elements describedin the following examples and modifications are merely examples, and arenot intended to limit the present invention.

FIG. 1A is a circuit diagram of a communication device 1 and an antennaelement 2 in a connection configuration 1 according to a preferredembodiment of the present invention. FIG. 1B is a circuit diagram of thecommunication device 1 and the antenna element 2 in a connectionconfiguration 2 according to a preferred embodiment of the presentinvention. As illustrated in FIGS. 1A and 1B, the communication device 1includes a front-end module 10, an RF signal processing circuit (RFIC)3, and a baseband signal processing circuit (BBIC) 4.

The RFIC 3 is an RF signal processing circuit that processeshigh-frequency signals transmitted and received by the antenna element2. Specifically, the RFIC 3 performs signal processing on ahigh-frequency signal (here, a high-frequency reception signal) inputfrom the antenna element 2 with the front-end module 10 interposedtherebetween, by down-conversion or other suitable processing, andoutputs a reception signal generated by the signal processing to theBBIC 4. Further, the RFIC 3 is also able to perform signal processing ona transmission signal input from the BBIC 4 by up-conversion or othersuitable processing, and is able to output a high-frequency signal(here, a high-frequency transmission signal) generated by the signalprocessing to a transmission side signal path.

In addition, in the present preferred embodiment, the RFIC 3 alsodefines and functions as a controller that controls connection ofswitches 11 and 12 (to be described later) of the front-end module 10based on a frequency band (band) to be used. Specifically, the RFIC 3switches between selection terminals connected to a common terminal forthe switches 11 and 12 in accordance with a control signal (not shown).Note that the controller may be provided outside the RFIC 3, or may beprovided in, for example, the front-end module 10 or the BBIC 4.

Next, a detailed configuration of the front-end module 10 will bedescribed.

As illustrated in FIGS. 1A and 1B, the front-end module 10 is areception system front-end circuit and includes the switches 11 and 12,filters 21A, 21B, and 21C, a reception amplifier circuit 41, andimpedance matching circuits 31 and 32.

The switch 11 is disposed between the impedance matching circuit 31 andthe filters 21A to 21C and is a first switch including a common terminal110 (first common terminal), and selection terminals 111 (firstselection terminal), 112 (second selection terminal), 113 and 114. Theswitch 11 exclusively switches among conduction between the selectionterminal 111 and the common terminal 110, conduction between theselection terminal 112 and the common terminal 110, and conductionbetween the selection terminal 113 and the common terminal 110. Further,the switch 11 switches between conduction and non-conduction between thecommon terminal 110 and the selection terminal 114.

In other words, the switch 11 is preferably a multiport ON switch thatis capable of simultaneously performing connection between the commonterminal 110 and the selection terminal 111 and connection between thecommon terminal 110 and the selection terminal 114, simultaneouslyperforming connection between the common terminal 110 and the selectionterminal 112 and connection between the common terminal 110 and theselection terminal 114, or simultaneously performing connection betweenthe common terminal 110 and the selection terminal 113 and connectionbetween the common terminal 110 and the selection terminal 114.

The filter 21A includes input/output terminals 211 (first input/outputterminal) and 212 (second input/output terminal), and is a first filterin which the input/output terminal 211 is connected to the selectionterminal 111, and has a Band A (first frequency band) as a pass band.

The filter 21B includes input/output terminals 213 (third input/outputterminal) and 214 (fourth input/output terminal), and is a second filterin which the input/output terminal 213 is connected to the selectionterminal 112, and has a Band B (second frequency band) as a pass band.

The filter 21C includes input/output terminals 215 and 216, and is afilter in which the input/output terminal 215 is connected to theselection terminal 113, and has a Band C as a pass band.

The switch 12 is a second switch including a common terminal 120 (secondcommon terminal), and selection terminals 121 (ninth selectionterminal), 122 (tenth selection terminal), and 123. The common terminal120 is connected to an input terminal of the reception amplifier circuit41, the selection terminal 121 is connected to the input/output terminal212 of the filter 21A, the selection terminal 122 is connected to theinput/output terminal 214 of the filter 21B, and the selection terminal123 is connected to the input/output terminal 216 of the filter 21C. Theswitch 12 is preferably an SP3T (Single Pole 3 Throw) switching circuitin which the common terminal 120 and one of the selection terminals 121to 123 are able to be connected.

The reception amplifier circuit 41 includes an output terminal connectedto the RFIC 3 and amplifies high-frequency signals input from thefilters 21A to 21C with the switch 12 interposed therebetween, and ispreferably a low noise amplifier circuit including, for example, atransistor or other suitable component.

In the above-described configuration, in the front-end module 10, one ofthe filters 21A to 21C is connected to the antenna element 2 and thereception amplifier circuit 41, by switching performed by the switches11 and 12.

The impedance matching circuit 32 is a first impedance matching circuitconnected to the selection terminal 114 different from the selectionterminals 111, 112, and 113 among the plurality of selection terminalsof the switch 11. Note that in FIGS. 1A and 1B, the impedance matchingcircuit 32 is a first parallel matching circuit connected between theselection terminal 114 and the ground, and is configured to beshunt-connected to the switch 11, but it is sufficient that one end ofthe impedance matching circuit 32 is connected to the selection terminal114, and a connection destination of another end may not necessarily begrounded.

The impedance matching circuit 31 is a second impedance matching circuitdisposed between the antenna element 2 and the switch 11, and connectedto the common terminal 110. Note that, although in FIGS. 1A and 1B, in acircuit configuration, the impedance matching circuit 31 is inserted inseries on a path connecting the antenna element 2 and the switch 11, itis sufficient that one end of the impedance matching circuit 31 isconnected to the above-described path, and a connection destination ofanother end may be grounded.

Each of the impedance matching circuits 31 and 32 has a circuitconfiguration in which, for example, circuit elements, such as aninductor and a capacitor, are connected in series or in parallel.

In this case, an impedance in the Band A when viewing the filter 21Aside from the common terminal 110 in a state in which the commonterminal 110 and only the selection terminal 111 among the selectionterminals 111 to 114 are connected is different from an impedance in theBand B when viewing the filter 21B side from the common terminal 110 ina state that the common terminal 110 and only the selection terminal 112among the selection terminals 111 to 114 are connected.

As illustrated in FIG. 1A, when the common terminal 110 and theselection terminal 111 are in the connection state and the commonterminal 110 and the selection terminal 112 are in the non-connectionstate, the common terminal 110 and the selection terminal 114 are in theconnection state (connection state 1). On the other hand, as illustratedin FIG. 1B, when the common terminal 110 and the selection terminal 112are in the connection state and the common terminal 110 and theselection terminal 111 are in the non-connection state, the commonterminal 110 and the selection terminal 114 are in the non-connectionstate (connection state 2).

As illustrated in FIG. 1A, when the switch 11 and the filter 21A areconnected, since the impedance matching circuit 32 is connected on apath connecting the switch 11 and the filter 21A with the selectionterminal 114 interposed therebetween (connection state 1), an impedancewhen viewing the filter 21A side from the common terminal 110 is able tobe adjusted to a predetermined impedance. On the other hand, asillustrated in FIG. 1B, when the switch 11 and the filter 21B areconnected, the impedance matching circuit 32 is not connected on thepath connecting the switch 11 and the filter 21A with the selectionterminal 114 interposed therebetween (connection state 2). In this case,although the impedance matching circuit 32 is not connected on theabove-described path, an impedance in the Band A when viewing the filter21A side from the common terminal 110 in a state that the commonterminal 110 and only the selection terminal 111 are connected isdifferent from an impedance in the Band B when viewing the filter 21Bside from the common terminal 110 in a state that the common terminal110 and only the selection terminal 112 are connected, and therefore, animpedance when viewing the filter 21B side from the common terminal 110is able to be adjusted to the predetermined impedance.

Note that, in the present preferred embodiment, “an impedance in theBand A is different from an impedance in the Band B” is defined suchthat an impedance obtained by averaging impedances in the Band A and animpedance obtained by averaging impedances in the Band B differ fromeach other by about 5% or more. Therefore, even if an impedance at apredetermined frequency in the Band A is equal or substantially equal toan impedance at a predetermined frequency in the Band B, for example, acase in which “an impedance in the band A is different from an impedancein the Band B” may also be assumed.

Note that the impedance matching circuit 31 may be omitted. Although animpedance when viewing each filter side from the common terminal 110 isadjusted to the above-described predetermined impedance by conductionand non-conduction of the impedance matching circuit 32, the impedancematching circuit 31 is a circuit that matches the predeterminedimpedance with a normalized impedance of the front-end module 10.Therefore, when the predetermined impedance is already the normalizedimpedance, the impedance matching circuit 31 is unnecessary.

Note that the “normalized impedance” is not limited to about 50Ω, forexample, and is sufficient to be equal or substantially equal to animpedance of a transmission system of the front-end module 10. In otherwords, a characteristic impedance of a transmission line defining thefront-end module 10 and a characteristic impedance of a transmissionline connected to the front-end module 10 are not limited to about 50Ω.

Further, the “normalized impedance” is not limited to an impedance equalor substantially equal to the impedance of the transmission system, andit may be an impedance matched with a circuit (the antenna element 2 inthe present preferred embodiment) connected to an input end of thefront-end module 10. For example, two impedances to be matched may be acomplex conjugate.

Further, while the front-end module 10 according to the presentpreferred embodiment includes the filters 21A to 21C, the number offilters, that is, the number of bands to be used may be two, or may befour or more, for example.

Further, although the reception amplifier circuit 41 is shared byhigh-frequency signals of the Band A, the Band B, and the Band C, byswitching the switch 12, a reception amplifier circuit may be providedfor each band. In this case, the switch 12 is unnecessary.

Further, although the configuration in which the front-end module 10according to the present preferred embodiment is connected to theantenna element 2 is illustrated, the front-end module 10 may notnecessarily be connected directly to the antenna element 2. For example,the front-end module 10 may be disposed with circuit elements, such as abranching filter, a switch, and a circulator, connected to the antennaelement 2 interposed therebetween.

FIG. 2 is a circuit diagram of a front-end module 510 according to acomparative example. The front-end module 510 illustrated in FIG. 2includes a switch 511, the switch 12, the filters 21A, 21B, and 21C, thereception amplifier circuit 41, and impedance matching circuits 531,532A, 532B, and 532C. The front-end module 510 according to thecomparative example differs from the front-end module 10 according tothe present preferred embodiment in a configuration of the switch 511and in that the impedance matching circuit is provided for each signalpath. Hereinafter, as a specific configuration of the front-end module510, a description of the same configuration as that of the front-endmodule 10 according to the present preferred embodiment will be omitted,and a different configuration is mainly described.

The switch 511 is a switching circuit disposed between the impedancematching circuit 531 and the filters 21A to 21C and includes the commonterminal 110 and the selection terminals 111, 112, and 113. The switch511 exclusively switches among conduction between the selection terminal111 and the common terminal 110, conduction between the selectionterminal 112 and the common terminal 110, and conduction between theselection terminal 113 and the common terminal 110.

The impedance matching circuit 532A is connected between the selectionterminal 111 and the filter 21A. The impedance matching circuit 532B isconnected between the selection terminal 112 and the filter 21B. Theimpedance matching circuit 532C is connected between the selectionterminal 113 and the filter 21C. In FIG. 2, each of the impedancematching circuits 532A to 532C has a circuit configuration in which thecircuit is inserted in series on a path connecting each selectionterminal of the switch 511 and each filter, but it is sufficient thatone end is connected to the path, and a connection destination ofanother end may be grounded.

In the front-end module 510 according to the comparative example, sincethe impedance matching circuits 532A, 532B and 532C are disposedcorresponding to the signal paths, an impedance in the Band A whenviewing the filter 21A side from the common terminal 110 in a state inwhich the common terminal 110 and only the selection terminal 111 areconnected, an impedance in the Band B when viewing the filter 21B sidefrom the common terminal 110 in a state in which the common terminal 110and only the selection terminal 112 are connected, and an impedance inthe Band C when viewing the filter 21C side from the common terminal 110in a state in which the common terminal 110 and only the selectionterminal 113 are connected are equal or substantially equal, and areadjusted to a predetermined impedance. However, in the front-end module510 according to the comparative example, since an individual impedancematching circuit is provided for each signal path, the number of circuitelements defining the impedance matching circuit increases, and thefront-end module 510 increases in size. Further, the impedance matchingcircuit provided for each signal path increases signal transmission lossin each signal path.

On the other hand, in the front-end module 10 according to the presentpreferred embodiment, since whether the impedance matching circuit 32connected to the selection terminal 114 is connected/not connected tothe signal path is switched by the switch 11 instead of individuallyproviding the impedance matching circuit for each signal path, thesignal transmission loss and the number of the circuit elements arereduced as compared to the front-end module 510 according to thecomparative example.

FIG. 3A is a circuit configuration diagram of a front-end module 10A andthe antenna element 2 in a connection configuration 1 according toExample 1. The front-end module 10A illustrated in FIG. 3A is a specificexample of the front-end module 10 according to a preferred embodimentof the present invention. The front-end module 10A includes the switches11 and 12, the filters 21A, 21B, and 21C, the reception amplifiercircuit 41, and the impedance matching circuits 31 and 32. The front-endmodule 10A according to Example 1 differs from the front-end module 10according to the above-described preferred embodiment in specificcircuit configurations of the respective impedance matching circuits 31and 32 and in that a wire connecting the switch 11 and each filter isexplicitly shown. Hereinafter, for the front-end module 10A according toExample 1, a description of the same configuration as that of thefront-end module 10 according to the above-described preferredembodiment will be omitted, and a different configuration is mainlydescribed.

The switches 11 and 12, the filters 21A, 21B, and 21C, the receptionamplifier circuit 41, and the impedance matching circuits 31 and 32,which define the front-end module 10A, are provided on a mountingsubstrate (not shown) or in the mounting substrate.

The impedance matching circuit 32 is a first impedance matching circuitconnected to the selection terminal 114 of the switch 11. Morespecifically, the impedance matching circuit 32 preferably includes aninductor connected between the selection terminal 114 and the ground,for example.

The impedance matching circuit 31 is a second impedance matching circuitdisposed between the antenna element 2 and the switch 11, and connectedto the common terminal 110. More specifically, the impedance matchingcircuit 31 includes an inductor which is preferably inserted in serieson a path connecting the antenna element 2 and the switch 11, forexample.

The filter 21A and the selection terminal 111 are connected by a wireL_(A) (first wire) provided on or in the mounting substrate. The filter21B and the selection terminal 112 are connected by a wire L_(B) (secondwire) provided on or in the mounting substrate. The filter 21C and theselection terminal 113 are connected by a wire L_(C) provided on or inthe mounting substrate.

Here, the wire L_(A) (first wire) is preferably longer than the wireL_(B) (second wire). Further, the wire L_(C) is preferably longer thanthe wire L_(B) (second wire). In the present example, the wire L_(A),the wire L_(B), and the wire L_(C) preferably have the same line width.

Here, an impedance in the Band A when viewing the filter 21A alone fromthe input/output terminal 211, an impedance in the Band B when viewingthe filter 21B alone from the input/output terminal 213, and animpedance in the Band C when viewing the filter 21C alone from theinput/output terminal 215 are set to be higher than a normalizedimpedance of the front-end module 10A.

FIG. 3B is a diagram illustrating a change in an impedance at each nodeof the front-end module 10A according to Example 1. In (a) of FIG. 3B,an impedance at the Band B of each node in a connection state 2 (a statein which the common terminal 110 and only the selection terminal 112 areconnected in the switch 11) is illustrated. Further, (b) of FIG. 3Billustrates an impedance at the Band A of each node in a connectionstate 1 (a state in which the common terminal 110 is connected to theselection terminal 111 and the common terminal 110 is connected to theselection terminal 114 in the switch 11).

As illustrated in (a) of FIG. 3B, an impedance in the Band B whenviewing the filter 21B alone from a connection node W2 (input/outputterminal 213) is set to be higher than the normalized impedance (e.g.,about 50Ω) as shown in an immittance chart below. Next, an impedancewhen viewing the filter 21B side from a connection node X2 between thewire L_(B) and the selection terminal 112 is made capacitive by shiftingalong the equiconductance circle clockwise due to parasitic capacitanceof the wire L_(B). Furthermore, an impedance when viewing the filter 21Bside from a connection node Y2 between the common terminal 110 and theimpedance matching circuit 31 is further shifted along theequiconductance circle clockwise due to parasitic capacitance of theswitch 11. Finally, an impedance when viewing the filter 21B side froman input side node Z2 of the impedance matching circuit 31 is set to beequal or substantially equal to the normalized impedance of thefront-end module 10A by shifting along an equiresistance circlecounterclockwise by a series inductor of the impedance matching circuit31. In this manner, in the connection state 2, by taking into accountthe shift to be capacitive by the wire L_(B) and the switch 11, and bysetting in advance the impedance in the Band B when viewing the filter21B alone to be higher than the normalized impedance, an impedance inthe Band B at an input end of the front-end module 10A is matched to thenormalized impedance.

On the other hand, as illustrated in (b) of FIG. 3B, an impedance in theBand A when viewing the filter 21A alone from a connection node W1(input/output terminal 211) is set to be higher than the normalizedimpedance (e.g., about 50Ω) as shown in an immittance chart below. Next,an impedance when viewing the filter 21A side from a connection node X1between the wire L_(A) and the selection terminal 111 is made capacitiveby shifting along the equiconductance circle clockwise due to parasiticcapacitance of the wire L_(A). At this time, since the wire L_(A) islonger than the wire L_(B), a capacitive shift amount of an impedancecaused by the wire L_(A) (a distance between W1 and X1 in the immittancechart of (b) of FIG. 3B) becomes larger than a capacitive shift amountof an impedance caused by the wire L_(B) (a distance between W2 and X2in the immittance chart of (a) of FIG. 3B). Furthermore, an impedancewhen viewing the filter 21A side from a connection node Y1 between thecommon terminal 110 and the impedance matching circuit 31 is furthershifted along the equiconductance circle clockwise due to the parasiticcapacitance of the switch 11. In other words, a capacitive shift amountof an impedance caused by the wire L_(A) and the switch 11 in theconnection state 1 (a distance between W1 and Y0 in the immittance chartof (b) of FIG. 3B) becomes larger than a capacitive shift amount of animpedance caused by the wire L_(B) and the switch 11 in the connectionstate 2 (a distance between W2 and Y2 in the immittance chart of (a) ofFIG. 3B). In this state, even in a case of shifting along theequiresistance circle counterclockwise by the series inductor of theimpedance matching circuit 31, an impedance when viewing the filter 21Aside from an input side node Z1 of the impedance matching circuit 31does not coincide with the normalized impedance of the front-end module10A. Accordingly, in the connection state 1 using a signal path of theBand A having a characteristic that the wire L_(A) is relatively long,the impedance matching circuit 32 is connected to the common terminal110. As a result, the impedance when viewing the filter 21A side fromthe connection node Y1 is able to be set to an impedance equal orsubstantially equal to that of Y2 in the connection state 2, since aposition Y0 in the immittance chart of (b) of FIG. 3B shifts along theequiconductance circle counterclockwise to Y1. Finally, the impedancewhen viewing the filter 21A side from the input side node Z1 of theimpedance matching circuit 31, is equal or substantially equal to thenormalized impedance of the front-end module 10A, by shifting along theequiresistance circle counterclockwise by the series inductorconfiguring the impedance matching circuit 31. In this manner, in theconnection state 1, by taking into account the shift to be capacitive bythe wire L_(A) and the switch 11, by setting in advance the impedance inthe Band A when viewing the filter 21A alone to be higher than thenormalized impedance, and by connecting the impedance matching circuit32 to the common terminal 110, an impedance in the Band A at an inputend of the front-end module 10A is matched to the normalized impedance.

As described above, according to the front-end module 10A of Example 1,in the connection state 2, the impedance when viewing the filter 21Bside from the common terminal 110 is shifted to be more capacitive thanan impedance of the filter 21B alone due to parasitic capacitance of thewire L_(B) and the switch 11.

Compared to this, in the connection state 1, an impedance when viewingthe filter 21A side from the common terminal 110 becomes an impedancewhich is shifted to be more capacitive than an impedance in theconnection state 2 due to parasitic capacitance of the wire L_(A) whichis longer than the wire L_(B) and the switch 11. However, since a shuntinductor of the impedance matching circuit 32 is connected, theimpedance when viewing the filter 21A side from the common terminal 110is shifted counterclockwise along the equiconductance circle on theimmittance chart, and thus is able to be set to be equal orsubstantially equal to the impedance when viewing the filter 21B sidefrom the common terminal 110 in the connection state 2.

FIG. 4 is a circuit configuration diagram of a front-end module 10B andthe antenna element 2 according to Modification 1 of a preferredembodiment of the present invention. The front-end module 10Billustrated in FIG. 4 includes the switches 11 and 12, the filters 21A,21B, and 21C, the reception amplifier circuit 41, the impedance matchingcircuits 31 and 32, and an impedance matching circuit 33C. The front-endmodule 10B according to Modification 1 is different from the front-endmodule 10 according to the above-described preferred embodiment in thatthe impedance matching circuit 33C is added. Hereinafter, for thefront-end module 10B according to Modification 1, a description of thesame configuration as that of the front-end module 10 according to theabove-described preferred embodiment will be omitted, and a differentconfiguration is mainly described.

The impedance matching circuit 33C is connected between the selectionterminal 113 and the filter 21C. In FIG. 4, the impedance matchingcircuit 33C has a circuit configuration in which the impedance matchingcircuit 33C is inserted in series on a path connecting the selectionterminal 113 and the filter 21C, but it is sufficient that one end ofthe impedance matching circuit 33C is connected to the path, and aconnection destination of another end thereof may be grounded.

Note that, FIG. 4 illustrates a state in which the common terminal 110and the selection terminal 111 are connected and the common terminal 110and the selection terminal 114 are connected (connection state 1).

When a high-frequency signal of the Band C is transmitted through theimpedance matching circuit 33C, the common terminal 110 and only theselection terminal 113 are connected, thus it is possible to correct acapacitive shift of an impedance due to parasitic capacitance of thewire L_(C) connecting the selection terminal 113 and the filter 21C andthe switch 11.

Note that, in this modification, the impedance matching circuit 33C isprovided in a signal path that transmits a high-frequency signal of theBand C among three signal paths that transmit high-frequency signals ofthe Band A, the Band B, and the Band C. In addition, an impedancematching circuit may be provided on a signal path that transmits ahigh-frequency signal of the Band A, or on a signal path that transmitsa high-frequency signal of the Band B. In other words, the followingconfiguration may be sufficient for the front-end module according to apreferred embodiment of the present invention. That is, an impedancematching circuit is not provided on at least one signal path (a pathconnecting a selection terminal of the switch 11 and a filter) among aplurality of signal paths included in the front-end module, and theimpedance matching circuit 32 that is able to be connected to any of thesignal paths is connected to a selection terminal of the switch 11.

FIG. 5A is a circuit diagram of a front-end module 10C and the antennaelement 2 in a connection configuration 1 according to Modification 2 ofa preferred embodiment of the present invention. Additionally, FIG. 5Bis a circuit diagram of the front-end module 10C and the antenna element2 in a connection configuration 2 according to Modification 2. FIG. 5Cis a circuit configuration diagram of the front-end module 10C and theantenna element 2 in a connection configuration 3 according toModification 2. As illustrated in FIGS. 5A to 5C, the front-end module10C includes a switch 11C, the switch 12, the filters 21A, 21B and 21C,the reception amplifier circuit 41, the impedance matching circuit 31,and impedance matching circuits 32A and 32B. As compared to thefront-end module 10 according to the above-described preferredembodiment, the front-end module 10C according to the presentmodification differs in a configuration of the switch 11C and theimpedance matching circuits connected thereto. Hereinafter, for thefront-end module 10C according to the present modification, the samedescription as that of the front-end module 10 according to theabove-described preferred embodiment will be omitted, and a differentconfiguration is mainly described.

The switch 11C is disposed between the impedance matching circuit 31 andthe filters 21A to 21C, and is a first switch including the commonterminal 110 (first common terminal), and the selection terminals 111(first selection terminal), 112 (second selection terminal), 113, 114(third selection terminals), 115 (fifth selection terminal) and 116(sixth selection terminal). The common terminal 110 and the selectionterminal 115 are connected.

The switch 11C exclusively switches among (1) conduction between theselection terminal 111 and the common terminal 110, (2) conductionbetween the selection terminal 112 and the common terminal 110, and (3)conduction between the selection terminal 113 and the common terminal110. More specifically, as a conduction configuration between theselection terminal 111 and the common terminal 110, one of connectionbetween the selection terminal 111 and the common terminal 110, orconduction between the selection terminal 111 and the common terminal110 via the selection terminal 116, the impedance matching circuit 32B,and the selection terminal 115 is selected. As a conductionconfiguration between the selection terminal 112 and the common terminal110, one of connection between the selection terminal 112 and the commonterminal 110, or conduction between the selection terminal 112 and thecommon terminal 110 via the selection terminal 116, the impedancematching circuit 32B, and the selection terminal 115 is selected. As aconduction configuration between the selection terminal 113 and thecommon terminal 110, one of connection between the selection terminal113 and the common terminal 110, or conduction between the selectionterminal 113 and the common terminal 110 via the selection terminal 116,the impedance matching circuit 32B, and the selection terminal 115 isselected. Further, the switch 11C switches between conduction andnon-conduction between the selection terminal 114 and the commonterminal 110. In other words, the switch 11C is a multiport ON switchcapable of simultaneously connecting the common terminal and theplurality of selection terminals and connecting the selection terminalsto each other to enable the above-described conduction configurations.

The impedance matching circuit 32A is a first parallel matching circuitconnected between the selection terminal 114 among the plurality ofselection terminals and the ground. By conduction between the selectionterminal 114 and the common terminal 110, the impedance matching circuit32A is able to be shunt-connected on a path connecting the commonterminal 110 and each filter. Therefore, it is possible to change animpedance when viewing the filter side from the common terminal 110 to apredetermined impedance.

Further, the impedance matching circuit 32B is a first series matchingcircuit connected between the selection terminal 115 and the selectionterminal 116 among the plurality of selection terminals. When theselection terminal 111 and the selection terminal 116 are connected, theimpedance matching circuit 32B is inserted in series between theselection terminal 111 and the common terminal 110, when the selectionterminal 112 and the selection terminal 116 are connected, the impedancematching circuit 32B is inserted in series between the selectionterminal 112 and the common terminal 110, and when the selectionterminal 113 and the selection terminal 116 are connected, the impedancematching circuit 32B is inserted in series between the selectionterminal 113 and the common terminal 110.

Note that each of the impedance matching circuits 32A and 32B preferablyhas a circuit configuration in which, for example, circuit elements,such as inductors and capacitors, are connected in series or inparallel.

For example, as illustrated in FIG. 5A, when a high-frequency signal ofthe Band A is transmitted, the common terminal 110 and the selectionterminal 111 are connected, the common terminal 110 and the selectionterminal 114 are connected, and the common terminal 120 and theselection terminal 121 are connected (connection configuration 1). Thus,a path connecting the antenna element 2, the impedance matching circuit31, the switch 11C, the filter 21A, the switch 12, and the receptionamplifier circuit 41 is provided, and the impedance matching circuit 32Ais shunt-connected to the path.

Further, for example, as illustrated in FIG. 5B, when a high-frequencysignal of Band B is transmitted, the selection terminal 112 and theselection terminal 116 are connected, and the common terminal 120 andthe selection terminal 122 are connected (connection configuration 2).Thus, a path connecting the antenna element 2, the impedance matchingcircuit 31, the impedance matching circuit 32B (switch 11C), the filter21B, the switch 12, and the reception amplifier circuit 41 is provided,and the impedance matching circuit 32B is inserted in series on thepath.

For example, as illustrated in FIG. 5C, when a high-frequency signal ofBand C is transmitted, the selection terminal 113 and the selectionterminal 116 are connected, the common terminal 110 and the selectionterminal 114 are connected, and the common terminal 120 and theselection terminal 123 are connected (a connection configuration 3).Thus, a path connecting the antenna element 2, the impedance matchingcircuit 31, the impedance matching circuit 32B (switch 11C), the filter21C, the switch 12, and the reception amplifier circuit 41 is provided,and the impedance matching circuit 32B is inserted in series on thepath, and the impedance matching circuit 32A is shunt-connected to thepath.

In the connection configurations described above, in the front-endmodule 10C, one of the filters 21A to 21C is connected to the antennaelement 2 and the reception amplifier circuit 41 by switching theswitches 11C and 12. Further, since the impedance matching circuit 32Bis connected to the selection terminals 115 and 116 of the switch 11Cand the impedance matching circuit 32A is connected to the selectionterminal 114, the impedance matching circuits 32A and 32B are able to beselectively added to a selected signal path without adding an impedancematching circuit for each signal path in which each of the filters 21Ato 21C is disposed. Thus, the impedance when viewing the filter sidefrom the common terminal 110 is able to be matched in a wide band with ahigh degree of accuracy.

Thus, for example, depending on three signal transmission modes, such asselection of one of the filters 21A to 21C, a plurality of connectionconfigurations of impedance matching circuits including theabove-described connection configurations 1 to 3 are able to be selectedas appropriate.

Note that, in the present modification, the two impedance matchingcircuits 32A and 32B are preferably connected to the switch 11C, forexample, but a configuration in which only the impedance matchingcircuit 32B is connected to the switch 11C suffices.

FIG. 6A is a circuit diagram of a front-end module 10D and the antennaelement 2 in a connection configuration 1 according to Modification 3 ofa preferred embodiment of the present invention. Additionally, FIG. 6Bis a circuit diagram of the front-end module 10D and the antenna element2 in a connection configuration 2 according to Modification 3. FIG. 6Cis a circuit diagram of the front-end module 10D and the antenna element2 in a connection configuration 3 according to Modification 3. Asillustrated in FIGS. 6A to 6C, the front-end module 10D includes aswitch 11D, the switch 12, the filters 21A, 21B, and 21C, the receptionamplifier circuit 41, the impedance matching circuits 31 and 32A, and animpedance matching circuit 33A. As compared to the front-end module 10according to the above-described preferred embodiment, the front-endmodule 10D according to the present modification differs in aconfiguration of the switch 11D and an impedance matching circuitconnected thereto. Hereinafter, for the front-end module 10D accordingto the present modification, the same description as that of thefront-end module 10 according to the above-described preferredembodiment will be omitted, and a different configuration is mainlydescribed.

The switch 11D is disposed between the impedance matching circuit 31 andthe filters 21A to 21C, and is a first switch including the commonterminal 110 (first common terminal), and the selection terminals 111(first selection terminal), 112 (second selection terminal), 113, 114(third selection terminals), and 117 (fourth selection terminal).

The switch 11D is a multiport ON switch which is capable of exclusivelyswitching among conduction between the selection terminal 111 and thecommon terminal 110, conduction between the selection terminal 112 andthe common terminal 110, conduction between the selection terminal 113and the common terminal 110, capable of switching between conduction andnon-conduction between the selection terminal 114 and the commonterminal 110, and capable of switching between conduction andnon-conduction between the selection terminal 117 and the commonterminal 110.

The impedance matching circuit 32A is a first parallel matching circuitconnected between the selection terminal 114 among the plurality ofselection terminals and the ground. By conduction between the selectionterminal 114 and the common terminal 110, the impedance matching circuit32A is able to be shunt-connected on a path connecting the commonterminal 110 and each filter. Therefore, it is possible to change animpedance when viewing the filter side from the common terminal 110 to apredetermined impedance.

The impedance matching circuit 33A is a second parallel matching circuitconnected between the selection terminal 117 among the plurality ofselection terminals and the ground. By conduction between the selectionterminal 117 and the common terminal 110, the impedance matching circuit33A is able to be shunt-connected on the path connecting the commonterminal 110 and each filter. Therefore, it is possible to change animpedance when viewing the filter side from the common terminal 110 to apredetermined impedance.

Note that each of the impedance matching circuits 32A and 33A preferablyhas a circuit configuration in which, for example, circuit elements,such as inductors and capacitors, are connected in series or inparallel.

For example, as illustrated in FIG. 6A, when a high-frequency signal ofthe Band A is transmitted, the common terminal 110 and the selectionterminal 111 are connected, the common terminal 110 and the selectionterminal 114 are connected, and the common terminal 120 and theselection terminal 121 are connected (connection configuration 1). Thus,a path connecting the antenna element 2, the impedance matching circuit31, the switch 11D, the filter 21A, the switch 12, and the receptionamplifier circuit 41 is provided, and the impedance matching circuit 32Ais shunt-connected to the path.

Further, for example, as illustrated in FIG. 6B, when a high-frequencysignal of the Band B is transmitted, the common terminal 110 and theselection terminal 112 are connected, the common terminal 110 and theselection terminal 114 are connected, the common terminal 110 and theselection terminal 117 are connected, and the common terminal 120 andthe selection terminal 122 are connected (connection configuration 2).Thus, a path connecting the antenna element 2, the impedance matchingcircuit 31, the switch 11D, the filter 21B, the switch 12, and thereception amplifier circuit 41 is provided, and the impedance matchingcircuits 32A and 33A are shunt-connected to the path.

Further, for example, as illustrated in FIG. 6C, when a high-frequencysignal of the Band C is transmitted, the common terminal 110 and theselection terminal 113 are connected, the common terminal 110 and theselection terminal 117 are connected, and the common terminal 120 andthe selection terminal 123 are connected (connection configuration 3).Thus, a path connecting the antenna element 2, the impedance matchingcircuit 31, the switch 11D, the filter 21C, the switch 12, and thereception amplifier circuit 41 is provided, and the impedance matchingcircuit 33A is shunt-connected to the path.

In the connection configuration described above, in the front-end module10D, one of the filters 21A to 21C is connected to the antenna element 2and the reception amplifier circuit 41 by switching the switches 11D and12. Further, since the impedance matching circuit 32A is connected tothe selection terminal 114 of the switch 11D and the impedance matchingcircuit 33A is connected to the selection terminal 117, the impedancematching circuits 32A and 33A is able to be selectively added to aselected signal path without adding an impedance matching circuit foreach signal path in which each of the filters 21A to 21C is disposed.Thus, the impedance when viewing the filter side from the commonterminal 110 is able to be matched in a wide band with a high degree ofaccuracy.

Thus, for example, depending on three signal transmissionconfigurations, such as selection of one of the filters 21A to 21C, aplurality of types of connection configurations of impedance matchingcircuits including the above-described connection configurations areable to be selected as appropriate.

Note that, in the present modification, the switch 11D is connected tothe two impedance matching circuits 32A and 33A, but three or more shuntconnection impedance matching circuits may be connected corresponding tothree or more selection terminals. The larger number of connections ofthe shunt connection impedance matching circuits makes it possible tomatch output of the impedance when viewing the filter side from thecommon terminal 110 with higher accuracy.

FIG. 7A is a circuit diagram of a front-end module 10E and the antennaelement 2 in a connection configuration 1 according to Modification 4 ofa preferred embodiment of the present invention. Additionally, FIG. 7Bis a circuit diagram of the front-end module 10E and the antenna element2 in a connection configuration 2 according to Modification 4. FIG. 7Cis a circuit diagram of the front-end module 10E and the antenna element2 in a connection configuration 3 according to Modification 4. Asillustrated in FIGS. 7A to 7C, the front-end module 10E includes aswitch 11E, the switch 12, the filters 21A, 21B, and 21C, the receptionamplifier circuit 41, the impedance matching circuits 31 and 32B, and animpedance matching circuit 33B. As compared to the front-end module 10according to the above-described preferred embodiment, the front-endmodule 10E according to the present modification differs in aconfiguration of the switch 11E and an impedance matching circuitconnected thereto. Hereinafter, for the front-end module 10E accordingto the present modification, the same description as that of thefront-end module 10 according to the above-described preferredembodiment will be omitted, and a different configuration is mainlydescribed.

The switch 11E is disposed between the impedance matching circuit 31 andthe filters 21A to 21C, and is a first switch including the commonterminal 110 (first common terminal) and the selection terminals 111(first selection terminal), 112 (second selection terminal), 113, 115(fifth selection terminal), 116 (sixth selection terminal), 118 (eighthselection terminal), and 119 (seventh selection terminal). The selectionterminal 116 and the selection terminal 119 are connected.

The switch 11E exclusively switches among conduction between theselection terminal 111 and the common terminal 110, conduction betweenthe selection terminal 112 and the common terminal 110, and conductionbetween the selection terminal 113 and the common terminal 110. Morespecifically, as a conduction configuration between the selectionterminal 111 and the common terminal 110, one of the following isselected: connection between the selection terminal 111 and the commonterminal 110, conduction between the selection terminal 111 and thecommon terminal 110 via the selection terminal 116, the impedancematching circuit 32B, and the selection terminal 115, conduction betweenthe selection terminal 111 and the common terminal 110 via the selectionterminal 116, the selection terminal 119, the impedance matching circuit33B, and the selection terminal 118, and conduction between theselection terminal 111 and the common terminal 110 via the selectionterminal 118, the impedance matching circuit 33B, the selection terminal119, the selection terminal 116, the impedance matching circuit 32B, andthe selection terminal 115. As a conduction configuration between theselection terminal 112 and the common terminal 110, one of the followingis selected: connection between the selection terminal 112 and thecommon terminal 110, conduction between the selection terminal 112 andthe common terminal 110 via the selection terminal 116, the impedancematching circuit 32B, and the selection terminal 115, conduction betweenthe selection terminal 112 and the common terminal 110 via the selectionterminal 119, the impedance matching circuit 33B, and the selectionterminal 118, and (iv) conduction between the selection terminal 112 andthe common terminal 110 via the selection terminal 118, the impedancematching circuit 33B, the selection terminal 119, the selection terminal116, the impedance matching circuit 32B, and the selection terminal 115.As a conduction configuration between the selection terminal 113 and thecommon terminal 110, one of the following is selected: connectionbetween the selection terminal 113 and the common terminal 110,conduction between the selection terminal 113 and the common terminal110 via the selection terminal 116, the impedance matching circuit 32B,and the selection terminal 115, conduction between the selectionterminal 113 and the common terminal 110 via the selection terminal 116,the selection terminal 119, the impedance matching circuit 33B, and theselection terminal 118, and conduction between the selection terminal113 and the common terminal 110 via the selection terminal 118, theimpedance matching circuit 33B, the selection terminal 119, theselection terminal 116, the impedance matching circuit 32B, and theselection terminal 115. In other words, the switch 11E is a multiport ONswitch capable of simultaneously connecting the common terminal and theplurality of selection terminals and connecting the selection terminalsto each other to achieve the above-described conduction configuration.

The impedance matching circuit 32B is a first series matching circuitconnected between the selection terminal 115 and the selection terminal116 among the plurality of selection terminals. By connecting the commonterminal 110 and the selection terminal 115 and connecting the selectionterminal 111 and the selection terminal 116, the impedance matchingcircuit 32B is inserted in series between the selection terminal 111 andthe common terminal 110. Further, by connecting the common terminal 110and the selection terminal 115 and connecting the selection terminal 112and the selection terminal 116, the impedance matching circuit 32B isinserted in series between the selection terminal 112 and the commonterminal 110. Further, by connecting the common terminal 110 and theselection terminal 115 and connecting the selection terminal 113 and theselection terminal 116, the impedance matching circuit 32B is insertedin series between the selection terminal 113 and the common terminal110.

The impedance matching circuit 33B is a second series matching circuitconnected between the selection terminal 118 and the selection terminal119 among the plurality of selection terminals. By connecting the commonterminal 110 and the selection terminal 118 and connecting the selectionterminal 111 and the selection terminal 119, the impedance matchingcircuit 33B is inserted in series between the selection terminal 111 andthe common terminal 110. Further, by connecting the common terminal 110and the selection terminal 118 and connecting the selection terminal 112and the selection terminal 119, the impedance matching circuit 33B isinserted in series between the selection terminal 112 and the commonterminal 110. Further, by connecting the common terminal 110 and theselection terminal 118 and connecting the selection terminal 113 and theselection terminal 119, the impedance matching circuit 33B is insertedin series between the selection terminal 113 and the common terminal110. Further, by connecting the common terminal 110 and the selectionterminal 118 and connecting the selection terminal 111 and the selectionterminal 115, a series-connected circuit including the impedancematching circuits 32B and 33B is inserted in series between theselection terminal 111 and the common terminal 110. Further, byconnecting the common terminal 110 and the selection terminal 118 andconnecting the selection terminal 112 and the selection terminal 115,the series-connected circuit including the impedance matching circuits32B and 33B is inserted in series between the selection terminal 112 andthe common terminal 110. Further, by connecting the common terminal 110and the selection terminal 118 and connecting the selection terminal 113and the selection terminal 115, the series-connected circuit includingthe impedance matching circuits 32B and 33B is inserted in seriesbetween the selection terminal 113 and the common terminal 110.

Note that each of the impedance matching circuits 32B and 33B preferablyhas a circuit configuration in which, for example, circuit elements,such as inductors and capacitors, are connected in series or inparallel.

For example, as illustrated in FIG. 7A, when a high-frequency signal ofthe Band A is transmitted, the common terminal 110 and the selectionterminal 115 are connected, the selection terminal 116 and the selectionterminal 111 are connected, and the common terminal 120 and theselection terminal 121 are connected (connection configuration 1). Thus,a path connecting the antenna element 2, the impedance matching circuit31, the impedance matching circuit 32B (switch 11E), the filter 21A, theswitch 12, and the reception amplifier circuit 41 is provided, and theimpedance matching circuit 32B is inserted in series on the path.

Further, for example, as illustrated in FIG. 7B, when a high-frequencysignal of the Band B is transmitted, the common terminal 110 and theselection terminal 118 are connected, the selection terminal 119 and theselection terminal 112 are connected, and the common terminal 120 andthe selection terminal 122 are connected (connection configuration 2).Thus, a path connecting the antenna element 2, the impedance matchingcircuit 31, the impedance matching circuit 33B (switch 11E), the filter21B, the switch 12, and the reception amplifier circuit 41 is provided,and the impedance matching circuit 33B is inserted in series on thepath.

Further, for example, as illustrated in FIG. 7C, when a high-frequencysignal of the Band C is transmitted, the common terminal 110 and theselection terminal 118 are connected, the selection terminal 115 and theselection terminal 113 are connected, and the common terminal 120 andthe selection terminal 123 are connected (connection configuration 3).Thus, a path connecting the antenna element 2, the impedance matchingcircuit 31, the impedance matching circuits 33B and 32B (switch 11E),the filter 21C, the switch 12, and the reception amplifier circuit 41 isprovided, and a series-connected circuit configured with the impedancematching circuits 33B and 32B is inserted in series on the path.

In the connection configuration described above, in the front-end module10E, one of the filters 21A to 21C is connected to the antenna element 2and the reception amplifier circuit 41 by switching the switches 11E and12. Further, since the impedance matching circuit 32B is connected tothe selection terminals 115 and 116 of the switch 11E and the impedancematching circuit 33B is connected to the selection terminals 118 and119, the impedance matching circuits 32B and 33B is able to beselectively added to a selected signal path without adding an impedancematching circuit for each signal path in which each of the filters 21Ato 21C is disposed. Thus, the impedance when viewing the filter sidefrom the common terminal 110 is able to be matched in a wide band with ahigh degree of accuracy.

Thus, for example, depending on three signal transmissionconfigurations, such as selection of one of the filters 21A to 21C, aplurality of types of connection configurations of impedance matchingcircuits including the above-described connection configurations 1 to 3are able be selected as appropriate.

Note that, in the present modification, the two impedance matchingcircuits 32B and 33B are preferably connected to the switch 11E, butthree or more series-inserted impedance matching circuits may beconnected. The larger number of connections of the series-insertedimpedance matching circuits makes it possible to match output of theimpedance when viewing the filter side from the common terminal 110 withhigher accuracy.

While front-end modules and communication devices according to thepresent invention have been described with reference to the preferredembodiments, the example, and the modifications, the present inventionis not limited to the above-described preferred embodiments, theexample, and the modifications. Another preferred embodiment achieved bycombining appropriate elements in the above-described preferredembodiments, for example, and the modifications; a modification obtainedby applying various modifications made by those skilled in the artwithout departing from the scope of the present invention to theabove-described preferred embodiments; and various devices including thefront-end modules and the communication devices according to preferredembodiments of the present invention are included in the presentinvention.

Further, for example, in the front-end module 10 and the communicationdevice 1 according to the above-described preferred embodiment, aninductor or a capacitor may be connected between the respectiveelements. Note that the inductor may include a wiring inductor definedby a wire connecting the respective elements.

Further, although the front-end module 10 according to theabove-described preferred embodiment is described as an example of afront-end circuit of a reception system, the front-end module 10 may bea front-end circuit of a transmission system. In this case, atransmission amplifier circuit, such as a power amplifier, is providedinstead of the reception amplifier circuit. Furthermore, a front-endcircuit including both of a reception signal path and a transmissionsignal path may be used.

Preferred embodiments of the present invention and modifications thereofare widely applicable to communication devices, such as a cellularphone, for example, as a small front-end module and communicationdevices with impedance matching which are able to be applied to amulti-band system.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A front-end module comprising: a first switchincluding a first common terminal and a plurality of selectionterminals; a first filter including a first frequency band as a passband, a first input/output terminal, and a second input/output terminal,the first input/output terminal being connected to a first selectionterminal among the plurality of selection terminals; a second filterincluding a second frequency band different from the first frequencyband as a pass band, a third input/output terminal, and a fourthinput/output terminal, the third input/output terminal being connectedto a second selection terminal among the plurality of selectionterminals; and a first impedance matching circuit connected to one ormore selection terminals different from the first selection terminal andthe second selection terminal among the plurality of selectionterminals; wherein an impedance in the first frequency band when viewinga first filter side from the first common terminal in a state in whichthe first common terminal is connected to only the first selectionterminal among the plurality of selection terminals is different from animpedance in the second frequency band when viewing a second filter sidefrom the first common terminal in a state in which the first commonterminal is connected to only the second selection terminal among theplurality of selection terminals; when the first common terminal is in aconnection state with the first selection terminal and the first commonterminal is in a non-connection state with the second selectionterminal, the first common terminal is in a connection state with oneselection terminal among the one or more selection terminals; and whenthe first common terminal is in a connection state with the secondselection terminal and the first common terminal is in a non-connectionstate with the first selection terminal, the first common terminal is ina non-connection state with the one selection terminal.
 2. The front-endmodule according to claim 1, further comprising a second impedancematching circuit connected to the first common terminal.
 3. Thefront-end module according to claim 1, wherein a first wire connectingthe first filter and the first selection terminal is longer than asecond wire connecting the second filter and the second selectionterminal; an impedance in the first frequency band when viewing thefirst filter alone from the first input/output terminal and an impedancein the second frequency band when viewing the second filter alone fromthe third input/output terminal are higher than a normalized impedanceof the front-end module; and the first impedance matching circuitincludes an inductor connected between the one or more selectionterminals and a ground.
 4. The front-end module according to claim 1,wherein the first impedance matching circuit includes: a first parallelmatching circuit connected between a third selection terminal among theplurality of selection terminals and a ground; and the first switchexclusively switches between conduction between the first selectionterminal and the first common terminal and conduction between the secondselection terminal and the first common terminal, and switches betweenconduction and non-conduction between the third selection terminal andthe first common terminal.
 5. The front-end module according to claim 4,wherein the first impedance matching circuit further includes: a secondparallel matching circuit connected between a fourth selection terminalamong the plurality of selection terminals and a ground; and the firstswitch exclusively switches between conduction between the firstselection terminal and the first common terminal and conduction betweenthe second selection terminal and the first common terminal, switchesbetween conduction and non-conduction between the third selectionterminal and the first common terminal, and switches between conductionand non-conduction between the fourth selection terminal and the firstcommon terminal.
 6. The front-end module according to claim 1, whereinthe first impedance matching circuit includes: a first series matchingcircuit connected between a fifth selection terminal and a sixthselection terminal among the plurality of selection terminals; and thefirst switch exclusively switches between one of connection between thefirst selection terminal and the first common terminal and conductionbetween the first selection terminal and the first common terminal viathe sixth selection terminal, the first series matching circuit, and thefifth selection terminal, and one of connection between the secondselection terminal and the first common terminal and conduction betweenthe second selection terminal and the first common terminal via thesixth selection terminal, the first series matching circuit, and thefifth selection terminal.
 7. The front-end module according to claim 6,wherein the first impedance matching circuit further includes: a secondseries matching circuit connected between a seventh selection terminaland an eighth selection terminal among the plurality of selectionterminals; the sixth selection terminal and the seventh selectionterminal are connected to each other; the first switch exclusivelyswitches between one of connection between the first selection terminaland the first common terminal, conduction between the first selectionterminal and the first common terminal via the sixth selection terminal,the first series matching circuit, and the fifth selection terminal,conduction between the first selection terminal and the first commonterminal via the eighth selection terminal, the second series matchingcircuit, and the seventh selection terminal, and conduction between thefirst selection terminal and the first common terminal via the fifthselection terminal, the first series matching circuit, the sixthselection terminal, the seventh selection terminal, the second seriesmatching circuit, and the eighth selection terminal, and one ofconnection between the second selection terminal and the first commonterminal, conduction between the second selection terminal and the firstcommon terminal via the sixth selection terminal, the first seriesmatching circuit, and the fifth selection terminal, conduction betweenthe second selection terminal and the first common terminal via theeighth selection terminal, the second series matching circuit, and theseventh selection terminal, and conduction between the second selectionterminal and the first common terminal via the fifth selection terminal,the first series matching circuit, the sixth selection terminal, theseventh selection terminal, the second series matching circuit, and theeighth selection terminal.
 8. The front-end module according to claim 1,further comprising: a second switch including a second common terminal,a ninth selection terminal, and a tenth selection terminal; and anamplifier connected to the second common terminal; wherein the secondinput/output terminal and the ninth selection terminal are connected toeach other; the fourth input/output terminal and the tenth selectionterminal are connected to each other; and the second switch switchesbetween connection and non-connection between the amplifier and thefirst filter, and switches between connection and non-connection betweenthe amplifier and the second filter.
 9. A communication device,comprising: an RF signal processing circuit that processes ahigh-frequency signal received by an antenna element; and the front-endmodule according to claim 1 that transmits the high-frequency signalbetween the antenna element and the RF signal processing circuit. 10.The communication device according to claim 9, further comprising asecond impedance matching circuit connected to the first commonterminal.
 11. The communication device according to claim 9, wherein afirst wire connecting the first filter and the first selection terminalis longer than a second wire connecting the second filter and the secondselection terminal; an impedance in the first frequency band whenviewing the first filter alone from the first input/output terminal andan impedance in the second frequency band when viewing the second filteralone from the third input/output terminal are higher than a normalizedimpedance of the front-end module; and the first impedance matchingcircuit includes an inductor connected between the one or more selectionterminals and a ground.
 12. The communication device according to claim9, wherein the first impedance matching circuit includes: a firstparallel matching circuit connected between a third selection terminalamong the plurality of selection terminals and a ground; and the firstswitch exclusively switches between conduction between the firstselection terminal and the first common terminal and conduction betweenthe second selection terminal and the first common terminal, andswitches between conduction and non-conduction between the thirdselection terminal and the first common terminal.
 13. The communicationdevice according to claim 12, wherein the first impedance matchingcircuit further includes: a second parallel matching circuit connectedbetween a fourth selection terminal among the plurality of selectionterminals and a ground; and the first switch exclusively switchesbetween conduction between the first selection terminal and the firstcommon terminal and conduction between the second selection terminal andthe first common terminal, switches between conduction andnon-conduction between the third selection terminal and the first commonterminal, and switches between conduction and non-conduction between thefourth selection terminal and the first common terminal.
 14. Thecommunication device according to claim 9, wherein the first impedancematching circuit includes: a first series matching circuit connectedbetween a fifth selection terminal and a sixth selection terminal amongthe plurality of selection terminals; and the first switch exclusivelyswitches between one of connection between the first selection terminaland the first common terminal and conduction between the first selectionterminal and the first common terminal via the sixth selection terminal,the first series matching circuit, and the fifth selection terminal, andone of connection between the second selection terminal and the firstcommon terminal and conduction between the second selection terminal andthe first common terminal via the sixth selection terminal, the firstseries matching circuit, and the fifth selection terminal.
 15. Thecommunication device according to claim 14, wherein the first impedancematching circuit further includes: a second series matching circuitconnected between a seventh selection terminal and an eighth selectionterminal among the plurality of selection terminals; the sixth selectionterminal and the seventh selection terminal are connected to each other;the first switch exclusively switches between one of connection betweenthe first selection terminal and the first common terminal, conductionbetween the first selection terminal and the first common terminal viathe sixth selection terminal, the first series matching circuit, and thefifth selection terminal, conduction between the first selectionterminal and the first common terminal via the eighth selectionterminal, the second series matching circuit, and the seventh selectionterminal, and conduction between the first selection terminal and thefirst common terminal via the fifth selection terminal, the first seriesmatching circuit, the sixth selection terminal, the seventh selectionterminal, the second series matching circuit, and the eighth selectionterminal, and one of connection between the second selection terminaland the first common terminal, conduction between the second selectionterminal and the first common terminal via the sixth selection terminal,the first series matching circuit, and the fifth selection terminal,conduction between the second selection terminal and the first commonterminal via the eighth selection terminal, the second series matchingcircuit, and the seventh selection terminal, and conduction between thesecond selection terminal and the first common terminal via the fifthselection terminal, the first series matching circuit, the sixthselection terminal, the seventh selection terminal, the second seriesmatching circuit, and the eighth selection terminal.
 16. Thecommunication device according to claim 9, further comprising: a secondswitch including a second common terminal, a ninth selection terminal,and a tenth selection terminal; and an amplifier connected to the secondcommon terminal; wherein the second input/output terminal and the ninthselection terminal are connected to each other; the fourth input/outputterminal and the tenth selection terminal are connected to each other;and the second switch switches between connection and non-connectionbetween the amplifier and the first filter, and switches betweenconnection and non-connection between the amplifier and the secondfilter.